Apparatus for making open-hearth steel



Jan. 7, 1936. M. J. CONWAY APPARATUS FOR MAKING OPEN HEARTH STEEL FiledJune 20, 1934 5 Sheets-Sheet l 4. L-i F: 6- -E i i l i v I =i f- :i

WITNESSES Jan. 7, 1936. M. J. CONWAY APPARATUS FOR MAKING om HEARIHSTEEL Filed June 20, 1954 5 Sheets-Sheet 3 v a, I I fllllllllllll..||llIL I\ rllillllllllll IIIIIIIIIPI llllk Jan. 7, 1936.

M. J. CONWAY APPARATUS FOR MAKING OP EN HEARTH-STEEL 5 Sheets-Sheet 4Filed June 20, 1934 6 INVENTOR mn sa -:5

woo? v Jan. 7, 1936. M. J. CONWAY 2 APPARATUS FOR MAKING OPEN HEARTHSTEEL Filed June 20, 1934 5 Sheets-Sheet 5 M my mww Patented Jan. 7,1936 UNITED STATES PATENT OFFICE APPARATUS FOR MAKING OPEN-HEART STEELMartin J. Conway, Coatesville, Pa. Application June 20, 1934, Serial No.431,456

- n 12 Claims. This invention relates tothe manufacture of steel orproducts requiring a similar heat treatment and more particularly to animproved method and apparatus for manufacturing what is known asopen-hearth steel and is a continuaof rectangular shape, and burninggases which develop'most of the heat for the chemical reac-"' tions arepassed over them, first from one end of the furnace and then from theother, through ports located in each end of the furnace.

The products of combustion which develop from such firing are passed outof thefurnace'in the reverse order through the ports temporarily not inuse for the entrance of the heating gas and into chambers partly filledwith checker brick which absorb some of the sensible heat of theseproducts and from which they are passed onward into the furnace stack.At relatively short intervals these reversals are effected by shuttingoff. the gas and air at one end of the furnace and introducing themthrough the checker cliambers at the opposite end.

In passing througlf/the checker chambers the g'asesabsorb some of theheat stored in the checker bricks; and enterthe furnace with a highsensible heat, consequently producing a much higher temperature ofcombustion than can be obtained without preheating which is essential inorder to provide the temperatures required for the production ofopen-hearth steel. In accordance with the usual practice, the re-'versals are'efl'ected at intervals of from fifteen to thirty minutes andare repeated until, the oxidation of the charge has reached a desiredpoint. Among the disadvantages of such prior practice is the deleteriouseflect upon the steel of the constantly varying temperatures resultingfrom the periodical reversing of the firing. In addition considerabletime and heat are wasted during the reversing operations. This isdue'to'the reversals taking several minutes, and to the fact that thegases contained in the checker cham bers and uptakes at the time of thereversing of the firing in each direction are passed out of the stackwithout reaching the furnace.

A further disadvantage is that duplicate air and fuel supplyingapparatus in the way of burner ports and reversing valves are requiredat the. end of the combustion chamber and also corresponding duplicatesets of regenerators and reversing, valves in the exhaust passages. Suchduplication of parts materially adds to the initial 1 cost of thefurnace and due thereto and to the uneven heating conditions encounteredtogether with the complicated problems resulting from the reversingoperations, the maintenance of the furnace is made very costly. Inaddition considerable'valuable time as well as heat is lost whenrepairsare required, which is relatively frequently, and, as will beappreciated, this all adds to the cost of the steel.

With these and various other dimculties in mind it is an object of thisinvention to provide an improved method of producing open-hearth steelin accordance with which the steel is subjected to uniform orselectively regulated heating, whereby a considerable saving of time andoperating cost as well as improvement in the 26 product is effected. n FV Anotherobject is to providea furnace for practicingthis method inwhich there is no unnecessary duplication of parts and in which theheating is can'ied out in a continuous uninter- 30 rupted process. Thisgrflli yreduces the initial cost of the furnace and due to theuniformity of the heating the maintenance cost is likewise reduced. r

,Another object is to increase the life of the 36 furnace as well asincrease its output over that of a furnace of the prior type having anequivavarious other novel features and advantagw of the'invention willbe apparent when the followingdetailed description is read inconjunction 15 with the accompanyingdrawings of which Fig. 1 is a planview of a furnace designed to mac-- tice this invention; Fig. 2 avertical section taken on the line 'II-II of Fig. 1 showing in additioncertain optional features which may be utilized; Fig-file. verticalsection taken on the line Ill-III of Fig. 1; Fig.4 a vertical-sectiontaken on the line IV-IV of Fig. 1; Fig. 5 a horizontal section taken onthe lines V--V of Figs. 3

and 4; Fig. 6 a vertical section taken on the line to Figs 9 and of anend construction adapted for. use with 'producer gas, blast furnace gasor a mixture of gases such as blast furnace and coke-oven gas, etc.

In accordancewith the invention a furnace is provided in which one-wayfiring is. employed and with which recuperators are used for heating theair or air and fuel burned in the furnace, the furnace being designed atits firing end to provide a burner adapted to thoroughly mix the fueland air without regard to the customary necessary dimensions for exhaustgases which in the past has militated seriously against proper andefilcient firing. The other end of the furnace in turn is equipped witha suitable outlet,for conducting the products of combustioh into a slagpocket or chamber in which the solids carried by .such products from thecombustion chamber are permitted to collect and from whence the gas isdischarged into the recuperators free of such ingredients.

In practicing the invention the furnace is first lighted and brought upto charging temperature, during which period the recuperators throughwhich the fuel and air flow oppositely to the products of combustion aregradually elevated in temperature. When a proper temperature forcharging is provided the charge is placed in the.furnace and subjectedto a con-- tinuous uninterrupted uniform heat until its treatment of thecharge is completed.

To reiterate, according to the invention the furnace is fired from oneend only, being equipped for that purpose at its firing end with anaccuratelyand efliciently designed main burner port 5 and an auxiliaryburner port 6. The main burner port is adapted to supply most of thefuel-and air=utilized in the furnace and is preferably placed as low aspossible in order to sweep the hearth and sinter the materials inpreparing the hearth for the charge.'

The auxiliary ports 6, which may be eliminated if not required, orincreased in number if desired, depending upon the size of the furnace,are mounted on the roof I and preferably at a steep angle, so as todirect their supply of fuel and air at high velocity toward the metalcontained in the hearth in a fashion to maintain a uniform temperaturethroughout the furnace.

The roof 'I which constitutes the top of the combustion chamber It maybe plain or arched and made out of any suitable refractory material. Forsupport it is suspended from a series of cross-beams 8 which are coveredover with sheet steel or other suitable material in such a manner as toprovide a cooling chamber 9' extending over the entire roof of thecombustion chamber. To} permit a flow of cooling air to be circulatedthrough such chamber to cool both the roof and its supporting structure,openings II and I2 are provided at opposite ends of the furnace, andavent or connection I3 is located 5 on the top thereof for connecting itto any suitable suction device capable of providing the propercirculation.

Back of I the hearth 2 there is provided a down-draft passage I 4through which the products of cumbustion are conducted from the combustion chamber lll'into a slag pocket or chamber l6. This chamber isadapted to collect the solids carried out of the combustion chamber bythe hot gases, and from it such gases, free 15 of the ingredients, arepassed into a series of recuperators l1, l8 and I3 which are employed torecover the waste heat from such products and to utilize it inpreheating the air delivered to the combustion chamberby the burnerports 2;) Sand 6.

- The first of these recuperators consists of a substantial rectangularhousing-2l constructed of suitable refractory material such as fireclaybrick properly reinforced with steel buckstays '25 (not shown).Communicating with the wall of this housing adjacent the furnace in theupper mid=section thereof is a duct or tlmnel 26 leading from the slagpocket l6. Opposite the inlet of this duct as shown in detailsin Figs.3, 5, 6, 7 and 8 there is provided a series of honeycomb-like walls 20formed of somewhat spoolshape fire-proof tile or blocks 22 which aresupported by a transverse wall 23 located above the base of therecuperator, and extended to a second transverse wall 30 spaced from theroof of the recuperator.

As shown in Figs. '7 and 8 the blocks compris- -ing these intermediaryvertically disposed honeycomb-like walls 20 consist of a pair of 40square laterally spaced fiat end walls 22a. connected together bytubular center sections 22b, said square end sections being providedwith suitable interlocking means (not shown) for rigidly effecting theirassembly in the form of a wall. As illustrated these walls form a seriesof channels 24 opening into the inlet 26 and through which the wasteproducts are passed into an outlet duct or tunnel 43 connecting thisrecuperator with the next recuperator l8, and as will be appreciated byreason of the tubular sections in the blocks 22 thesegases are permittedto pass freely between such channels 24. Connected to the chamber 30formed in the recuperator below the transverse flow "block supportingwall 23 is an airduct 42 by which the outlet of recuperator I3 .isconnected to this recuperator and from this chamber the air is passedupwardly through openings 25 in the wall 23 between the end sections 22aof the blocks 22 and about the tubular sections 22b into a chamber 10formed by the transverse wall 30 passage 35. To provide'a definite pathfor the waste gasfrom this up-dra'ft passage 35 to the down-draftpassage 36 the middle section 39 of the roof of the recuperatoris'raised and the upper ends of the walls 32 and 33 are joined by acovered wall 40.

For passing the air through this intermediate recuperator from its airchamber 31 which is connected by a conduit or tunnel 4I- with theoutletof the last recuperator I9 and the chamber 38 which is connectedby a tunnel 42 with the inlet chamber 80 of recuperator .Il, a series oftiers of tubes 44, and 44a is mounted in the walls 3|, 32, 33 and 34,respectively, and to facilitate. the mounting of these tubes as well asfor cleaning them, the walls 32 and 33 in the center of the recuperatorI8 are spaced sufllciently far apart to form a chamber 40a in which aman may work. It is also contemplated, that suitable baffling (notshown) may be inserted in the various recuperators to channel the gasthrough them in such a way. as to bring about eflicient transfer of theheat from the exit gases to the preheated air for combustion.Furthermore, while tubes are shown in the recuperators for conductingthe air through them, any type or shape of passage may be used. so longas mixing of the exhaust gas and air is not permitted. I

From the lower end of the down-draft passage 36 in the recuperator I8 aflue tunnel 50 is connected to the bottom of the recuperator I9 andthrough it the waste gases are passed upwardly between verticallydisposed walls 45 to an outlet flue 45, horizontal baflles 41 beingarranged between the walls 45 to provide a more circuitous I path forthe incoming air.

To provide a fixed draft for the furnace the 'flue 46 is connected tothe inlet of a fan 48 which is operated by a motor 40 and has its outletin turn connected by a flue to 'a stack 5m, and for installations whereit is non-essential to pass all of the products of combustion throughthis recuperator, a by-pass stack connection I00 is connecteddirectlyfrom the tunnel 50 to the stack 5Ia, 'being provided with a damper I0lfor controlling the amount of gases passed through it. As illustratedbest in Fig. 5 the walls 45 are mounted in pairs and these pairs arespaced from each other to provide passages 52 for the passage of the airthrough the recuperator, the lower ends of the latter passages beingarranged to communicate with tunnel 4| leading to the air inlet ofrecuperator I 8 and their upper ends with a conduit 53 which isconnected to the outletof an air drafting fan 54 which is operated by amotor 55. 'As-shown, to take advantage of the heat absorbed by the airpassed through the cooling chamber 3 over the roof of the furnace, andalso to make use of the air drafting fan for'cooling theroofas well assupplying air. to the combustion chamber inthe furnace; the inlet'of thefan 54 is connectedto the vent I3 in the top of the furnace by a conduit55 having a draftingdamper 51 in it.

For communicating the air supplied by the fan 54 as it leaves the outletchamber I0 of recuper-' ator I! to' the burner ports 5 and 5. conduit ortunnel 58 is utilized.

In the operation of the furnace the products of combustion are drawnfrom the combustion chamber I0 by the drafting fan 43 through therecuperators I1, I3 and I9 in the path marked by the double-headedarrows in the drawings, which is traced from chamber I Ii through thepassage I4 into the slag pocket I6, thence by passage 26 into the upperwall of the recuperator II through which it is forced downwardly throughthe channels 24 and the tubular section's 22a of the baflle blocks 22into the down-draft through the joints which develop between the passage21 which carries it into the bottom of the up-draft passage 35 and therecuperator I8. 1 In this passage it passes by the tube 44a, thedown-draft passage 36, around the tubes 44 and by way of the passage orflue 50 into the bottom of recuperator I9 from whence it passes upwardlybetween the walls 45'into. the flue 45 and then by way of the fan 48into the flue 5| which carries it to the furnace stack and theatmosphere. 7 l

The air in turn is forced by fan 54 through recuperator I 0 by way ofpassage 52 into the chamber 31 of recuperator I8 from whence it passesthrough the tubes 44 and 4411. into chamber 33 and from there by passage42 into the chamber 50 of recuperator II. From this ohamher it passesthrough the channels 25 defined,

.by the walls into the chamber 10 and from thence by wayof duct 50=tothe burner ports 5 and 6. '3

As shown in Fig. 2, fuel is fed into the furnace by a passage 5| whichhas branches 62 and 63 running to the main and auxiliary ports 5 and 6.However, as shown in Figs. 9, 10, 11 and 12, the burner end of thefurnace may be differently constructed as required for handlingdifferent kinds of fuel.

In Figs. 9 and 10, a form of burner construction is illustrated for usewith coal tar, oils,

natural gas and oils, while in Figs. 11 and 12 a type of furnaceconstruction is shown for use with natural gas, coke oven gas, producergas, blast furnace gas, mixed gas and the like. In the latter, inlet 6Iais particularly adapted for producer gas.

As will be appreciated by those. skilled in the art, the tubular blocks22 employed in the first recuperator I! are made of some suitablerefractory material such as chrome or mullite which will not bedeleteriously affected by the products of combustion or the impuritiesin the form of oxides or slags which they carry.

It will also be appreciated, however,. that it is very difficult in viewof the great temperatures and great changes in temperature encounteredby such recuperators to maintain a sealed contact between the blocks. 22because of the considerable expansion and contraction which will -takeplace between them. Nevertheless it is air is passed therethrough at apressure .higher than atmosphere while, the waste gases are 5 passedthrough at a pressure below atmosphere, which in a construction of thistype would normally tend to produce a considerable. leakage' of .the airinto the waste gas products recuperator blocks as a result of the cracksformed by expansion and contraction.

To eliminate this condition, or in other words balance these pressures,an auxiliary fan I02 is provided which is equipped with 'a motor I03 andarranged with its inlet connected bya duct I04 with the air passage 42connecting the recupera tor I8 to therecuperator I1, and its outlet I04aconnected to a duct I05 which is projected into the tunnels 5Bin'a'manner to function as a jet tending to increase the suction on theair passing through the recuperator II, this arrangeone of a number ofwell-known constructions of this character and connected by suitabletubes I08 and I08 with the channels 25 between the top and bottom of therecuperators and the channels 24 defined by the walls 20. Thisregulator, as will be readily appreciated without necessarilydescribingthe details thereof, is connected to suitable control means I06connected to the supply circuit IIO of the fan motor I03 to so regulatethe operation of the fan I02 as to maintainthe desired air pressure inthe recuperator.

It will also be appreciated that by reason of the passages 24 in therecuperator II being made relatively large as illustrated, they providean unobstructed and free pmage permitting a slow movement of the gas ina general downward direction so that the gases effectively give up theirheat by radiation to the outer walls of the blocks 22 as well as to thesurface of the tubular sections 22b which are in direct contact with theair passing upward and around them and the channels formed between themand sections 2211. Such construction also militates against any clo ingof the recuperator by reason of any deposit which may not settle out ofthe waste products in the slag pockets settling in such channels. 1

In the second recuperator I8, due to the temperature of the gases beingsomewhat reduced by the time they reach the tubes I4 and a, the lattermay be made of diiferentmaterial than that used in the'formation ofblocks 22 in the recuperator l1, and preferably a material such ascarborundum which has a higher coefficient of conductivity than mulliteor chrome, while in recuperator I9 metal may be used to form the air andgas passage. Such metal will suflice for the construction and ispreferably used because of its high heat conducting qualities.

To provide a maximum efiiciency for the recuperators and a cost, thecross-section of the air and gas passages is reduced from the first tothe last recuperator in accordance with the variations'in the volume ofthe gas and air passing through them which vary as their temperatures.In their construction, consideration is also given to the control overthe speed of passage of the air andgas through them to afiord themaximum transfer of heat.

To provide for forcing air into the roof-cooling chamber 9 for coolingpurposes only a separate fan 8I disposed to be operatedby a motor 82 maybe mounted with its outlet connected by a conduit 83 with the duct 56, agate 84 being provided in the duct 83 for disconnecting it from the duct58 when the fan 54. is used.

To permit the operation of the fan 54 when the fan 8I is operated, ashut-01f gate 85 may be provided in duct 56 on the draft fan side of theduct 83, and an outlet gate 86 may be provided opposite thereto in 'duct56 for letting the inlet air enter the duct ahead of the regulatingvalve 51. When the fan 8| is operated the openings II and I2 are closedso that the cool air forced in the chamber 9 will be forced through theinterstices between the brickwork of the furnace roof and not only coolthe roof but also provide a shield on the underside of the roof toprotect the roof against the products of combustion inthe combustionchamber. As further precaution against injury to the roof fromoverheating, ventilator 'Il may be present in the given quantity ofcharge considerably increased. In addition, its cost of production ismaterially reduced by reason of the fact that the overhead accuratelyregulated and its quality by reason thereof improved as well as itsvolume from a.

cost incidental to the installation and mainte- 4 nance of the furnaceis materially reduced as well-as the fact that the time required forreducing a charge to the proper constituents is greatly lessenedinasmuch as the intermittent time losses due to varying reversals areeliminated.

In addition, among the detailed advantages of the invention is thesaving in cost efiected by the elimination of reversing valves,duplicate burners, double air regenerators and the like. Another isthe'saving in maintenance possible because of the longer life which thefurnace enjoys due to .the'uniform heating conditions under which itoperates. A further advantage is the greater economy obtained by meansof the greater heat efficiency flow from the unidirectional firing. In,addition, there are numerous other advantages which wi1l be apparent tothose s ed in the art.

While the furnace as illustrated and described constitutes an embodimentof the invention intended more particularly for refining steel, it willbe understood that the invention may be applied to other processes wherehigh temperatures are such as in the meltingof glass and the like.

According to the provisions of the patent statutes, I have explained theprinciple and mode of operation of my invention and have illustrated anddescribed what I now consider to represent 'its best embodiment.However, I desire to have it understood that within the scope of theappended claims the invention may be practiced otherwise than as"specifically illustrated and described.

I claim':

1. An open hearth furnace comprising a melting hearth forming the bottomwall of an enclosed heating chamber, heating means at one end of thechamber above the hearth embodying fuel and air supply means, means forwithdrawing the products of combustion at another end of said chamber,and means for preheating the air supply to the heating means by the heatof the products of combustion leaving the heating chamber includingmeans for balancing the pressure of the preheated air entering thefurnace and the products of combustion or waste gases leaving thefurnace chamber, said pressure balancing meansbeing responsive toandcontrolled by variations in the pressure of the waste gases orproducts of. combustion leaving the furnace chamber and the preheatedair entering said chamber.

2. In an open hearth furnace, the combina tion with a. melting chamberof a recuperator ducting waste gasesand air under pressure through saidrecuperator passages, and means responsive to the pressure differentialof the fluids in said recuperator passages for changing the pressure ofthe air to substantially the same pressure as the waste gases.

3. An industrialheating furnace comprising a heating chamber, heatingmeans at one end of the chamber above the hearth embodying fuel and airsupply means, a waste gas passage for withdrawing the products ofcombustion at "another end of said chamber, a recuperator communicatingwith said waste gas passage and with the air supply means and embodyingheat ex-,

change passages for the waste gases and air to be preheated, means formaintaining constant pressure of the air in said heat exchange passages,and means for increasing the volume of air delivered to the heatingchamber independently of said pressure controlling means.

4. An industrial heating furnace comprising a heating chamber, heatingmeans at one end of the chamber above the hearth embodying fuel and airsupply means, a waste gas passage for withdrawing the products ofcombustion at another end of said chamber, a recuperator communicatingwith said waste gas passage and with the air supply means and embodyingheat exchange passages for the waste gases and air to be preheated, apressure regulator operative in response to variations in the pressureof the gases, and air passing through, said heat exchange passages formaintaining a predetermined relation of the pressure in the waste gasand air passages.

5. An industrial heating furnace comprising a heating chamber, heatingmeans at one end of the chamber above the hearth embodying fuel and airsupply means, a waste gas passage for withdrawing the products ofcombustion at another end of said chamber, a recuperator communicatingwith said waste gas passage and with the air supply means and embodyingheat exchange passages for the waste gases and air to be preheated,air'pressure means connected to the air passages of the recuperator andalso.

directly to the air passage leading to the heating chamber, and pressureregulating means for automatically regulating the air pressure means tovary the volumes of air delivered to the air passages of .therecuperator and the air passage of the furnace chamber.

6. [in industrial heating furnace comprising a heating chamber, heatingmeans at one end of the chamber above the hearth embodying fuel and'airsupply means, a waste gas passage for withdrawingthe products ofcombustion at one end of said chamber, a recuperator communieating withsaid waste gas passage having heat exchange-passages for the waste gasand air supplied to the furnace chamber, a blower connected to therecuperator to supply air to the heat exchange passages, a motor forsaid blower, a

regulator responsive to the waste gas pressures combustion in theheating chamber, awaste gas passage for drawing the products ofcombustion from thefurnace chamber, a primary refractory recuperatorhaving heat exchange passages communicating with the waste gas and airdelivering passages of the furnace, a secondary metallic 5 recuperatorhaving heat exchange passages in communication with the heat exchangepassages of the first recuperator, means for delivering air underpressure to and from the secondary re- 7 cuperator to the primaryrecuperator, means 10 for exhausting the waste gases from the furnacechamber through said recuperators in the ordermentioned, and means forsupplying additional air to the first recuperator in accordance with adesired volume and pressure of the air passing of burners, fuel supplymeans therefor, air pas- 2o sages for delivering air to the burners tosupport combustion in the heating chamber, a waste gas passage fordrawing the products of combustion from the furnace chamber, a primaryrefractory recuperator having heat exchange passages com- 25 municatingwith the waste gas and air delivering passages of the furnace, asecondary metallic recuperator having heat exchange passages incommunication with the heat exchange passages of the first recuperator,means for delivering air 30 underpressure to and from themetallic-recuperator to the primary recuperator, means for exhaustingthe waste gases from the furnace chamberthrough the primary andsecondary recuperators in the order mentioned, and means 3 for supplyingadditional air to the heat exchange passages of the primary recuperatorand to the air passage leading from the recuperator to the furnacechamber.

9. In an industrial heating furnace, a heating 0 chamber, heating meanscomprising a plurality of burners, fuel supply means therefor, airpassages for delivering air to the burners to support combustion in theheating chamber, a waste gas passage for drawing the products ofcombustion 5 from the furnace chamber, a primary refractory recuperatorhaving heat exchange passages communicating with the waste gas and airdelivering passages of the furnace, a secondary metallic recuperatorhaving heat exchange passages in 50 communication with the heat exchangepassages of the first recuperator, means for delivering air underpressure to and from the metallic recuperator to primary recuperator,means for exhausting the waste gases from the furnace 55 chamber throughthe primary and secondary recuperators in the order mentioned, and meansfor balancing the pressure of the'air and waste gases in the heatexchange passages of the firstnamed recuperator. J

10. In an open hearth furnace, a heatingchamber, fuel burners andpreheatfair passages for said chamber, a waste gas passage leading fromsaicrchamber, a cooling chamber above the furnace, exhaust means'forsaid cooling cham- 65 her, a plurality of recuperators having heatexchange passages for successively receiving the waste gases from thefurnace chamber and delivering preheated air to support combustion insaid chamber, and means for drawing air 7 a waste gas passage leading 15r for said chamber,. a waste gas passage leading from said chamber, acooling chamber above the furnace, exhaust means for said coolingchamber, a plurality of recuperators having heat exchange passages forsuccessively receiving the waste gases from the furnace chamber anddelivering preheated air to support combustion in said chamber, meansfor drawing air through the cooling chamber above the furnace and.delivering it to the recuperators, and means for supplementing the airsupply after it has passed from the recuperators.

12. In an open hearth furnace, a heating chamber, fuelburners andpreheat air passages from said chamber, a cooling chamber above the ber,a plurality of recuperators having heat exchange passages forsuccessively receiving the waste gases from the furnace chamber anddelivering preheated air to support combustion in said chamber, meansfor drawing air through the cooling chamber above the furnace anddelivering it to the recuperators, and means for supplementing the airsupply to the recuperators and to the preheated air passage leading tothe furnace chamber. a MARTIN J. CONWAY.

